/* deflate.h -- internal compression state
 * Copyright (C) 1995-2010 Jean-loup Gailly
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/* WARNING: this file should *not* be used by applications. It is
   part of the implementation of the compression library and is
   subject to change. Applications should only use zlib.h.
 */

/* @(#) $Id$ */

#ifndef DEFLATE_H
#define DEFLATE_H

#include "zutil.h"

/* define NO_GZIP when compiling if you want to disable gzip header and
   trailer creation by deflate().  NO_GZIP would be used to avoid linking in
   the crc code when it is not needed.  For shared libraries, gzip encoding
   should be left enabled. */
#ifndef NO_GZIP
#define GZIP
#endif

/* ===========================================================================
 * Internal compression state.
 */

#define LENGTH_CODES 29
/* number of length codes, not counting the special END_BLOCK code */

#define LITERALS  256
/* number of literal bytes 0..255 */

#define L_CODES (LITERALS+1+LENGTH_CODES)
/* number of Literal or Length codes, including the END_BLOCK code */

#define D_CODES   30
/* number of distance codes */

#define BL_CODES  19
/* number of codes used to transfer the bit lengths */

#define HEAP_SIZE (2*L_CODES+1)
/* maximum heap size */

#define MAX_BITS 15
/* All codes must not exceed MAX_BITS bits */

#define INIT_STATE    42
#define EXTRA_STATE   69
#define NAME_STATE    73
#define COMMENT_STATE 91
#define HCRC_STATE   103
#define BUSY_STATE   113
#define FINISH_STATE 666
/* Stream status */

/* Data structure describing a single value and its code string. */
typedef struct ct_data_s {
	union {
		ush freq;	/* frequency count */
		ush code;	/* bit string */
	} fc;
	union {
		ush dad;	/* father node in Huffman tree */
		ush len;	/* length of bit string */
	} dl;
} FAR ct_data;

#define Freq fc.freq
#define Code fc.code
#define Dad  dl.dad
#define Len  dl.len

typedef struct static_tree_desc_s static_tree_desc;

typedef struct tree_desc_s {
	ct_data *dyn_tree;	/* the dynamic tree */
	int max_code;		/* largest code with non zero frequency */
	static_tree_desc *stat_desc;	/* the corresponding static tree */
} FAR tree_desc;

typedef ush Pos;
typedef Pos FAR Posf;
typedef unsigned IPos;

/* A Pos is an index in the character window. We use short instead of int to
 * save space in the various tables. IPos is used only for parameter passing.
 */

typedef struct internal_state {
	z_streamp strm;		/* pointer back to this zlib stream */
	int status;		/* as the name implies */
	Bytef *pending_buf;	/* output still pending */
	ulg pending_buf_size;	/* size of pending_buf */
	Bytef *pending_out;	/* next pending byte to output to the stream */
	uInt pending;		/* nb of bytes in the pending buffer */
	int wrap;		/* bit 0 true for zlib, bit 1 true for gzip */
	gz_headerp gzhead;	/* gzip header information to write */
	uInt gzindex;		/* where in extra, name, or comment */
	Byte method;		/* STORED (for zip only) or DEFLATED */
	int last_flush;		/* value of flush param for previous deflate call */

	/* used by deflate.c: */

	uInt w_size;		/* LZ77 window size (32K by default) */
	uInt w_bits;		/* log2(w_size)  (8..16) */
	uInt w_mask;		/* w_size - 1 */

	Bytef *window;
	/* Sliding window. Input bytes are read into the second half of the window,
	 * and move to the first half later to keep a dictionary of at least wSize
	 * bytes. With this organization, matches are limited to a distance of
	 * wSize-MAX_MATCH bytes, but this ensures that IO is always
	 * performed with a length multiple of the block size. Also, it limits
	 * the window size to 64K, which is quite useful on MSDOS.
	 * To do: use the user input buffer as sliding window.
	 */

	ulg window_size;
	/* Actual size of window: 2*wSize, except when the user input buffer
	 * is directly used as sliding window.
	 */

	Posf *prev;
	/* Link to older string with same hash index. To limit the size of this
	 * array to 64K, this link is maintained only for the last 32K strings.
	 * An index in this array is thus a window index modulo 32K.
	 */

	Posf *head;		/* Heads of the hash chains or NIL. */

	uInt ins_h;		/* hash index of string to be inserted */
	uInt hash_size;		/* number of elements in hash table */
	uInt hash_bits;		/* log2(hash_size) */
	uInt hash_mask;		/* hash_size-1 */

	uInt hash_shift;
	/* Number of bits by which ins_h must be shifted at each input
	 * step. It must be such that after MIN_MATCH steps, the oldest
	 * byte no longer takes part in the hash key, that is:
	 *   hash_shift * MIN_MATCH >= hash_bits
	 */

	long block_start;
	/* Window position at the beginning of the current output block. Gets
	 * negative when the window is moved backwards.
	 */

	uInt match_length;	/* length of best match */
	IPos prev_match;	/* previous match */
	int match_available;	/* set if previous match exists */
	uInt strstart;		/* start of string to insert */
	uInt match_start;	/* start of matching string */
	uInt lookahead;		/* number of valid bytes ahead in window */

	uInt prev_length;
	/* Length of the best match at previous step. Matches not greater than this
	 * are discarded. This is used in the lazy match evaluation.
	 */

	uInt max_chain_length;
	/* To speed up deflation, hash chains are never searched beyond this
	 * length.  A higher limit improves compression ratio but degrades the
	 * speed.
	 */

	uInt max_lazy_match;
	/* Attempt to find a better match only when the current match is strictly
	 * smaller than this value. This mechanism is used only for compression
	 * levels >= 4.
	 */
#define max_insert_length  max_lazy_match
	/* Insert new strings in the hash table only if the match length is not
	 * greater than this length. This saves time but degrades compression.
	 * max_insert_length is used only for compression levels <= 3.
	 */

	int level;		/* compression level (1..9) */
	int strategy;		/* favor or force Huffman coding */

	uInt good_match;
	/* Use a faster search when the previous match is longer than this */

	int nice_match;		/* Stop searching when current match exceeds this */

	/* used by trees.c: */
	/* Didn't use ct_data typedef below to supress compiler warning */
	struct ct_data_s dyn_ltree[HEAP_SIZE];	/* literal and length tree */
	struct ct_data_s dyn_dtree[2 * D_CODES + 1];	/* distance tree */
	struct ct_data_s bl_tree[2 * BL_CODES + 1];	/* Huffman tree for bit lengths */

	struct tree_desc_s l_desc;	/* desc. for literal tree */
	struct tree_desc_s d_desc;	/* desc. for distance tree */
	struct tree_desc_s bl_desc;	/* desc. for bit length tree */

	ush bl_count[MAX_BITS + 1];
	/* number of codes at each bit length for an optimal tree */

	int heap[2 * L_CODES + 1];	/* heap used to build the Huffman trees */
	int heap_len;		/* number of elements in the heap */
	int heap_max;		/* element of largest frequency */
	/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
	 * The same heap array is used to build all trees.
	 */

	uch depth[2 * L_CODES + 1];
	/* Depth of each subtree used as tie breaker for trees of equal frequency
	 */

	uchf *l_buf;		/* buffer for literals or lengths */

	uInt lit_bufsize;
	/* Size of match buffer for literals/lengths.  There are 4 reasons for
	 * limiting lit_bufsize to 64K:
	 *   - frequencies can be kept in 16 bit counters
	 *   - if compression is not successful for the first block, all input
	 *     data is still in the window so we can still emit a stored block even
	 *     when input comes from standard input.  (This can also be done for
	 *     all blocks if lit_bufsize is not greater than 32K.)
	 *   - if compression is not successful for a file smaller than 64K, we can
	 *     even emit a stored file instead of a stored block (saving 5 bytes).
	 *     This is applicable only for zip (not gzip or zlib).
	 *   - creating new Huffman trees less frequently may not provide fast
	 *     adaptation to changes in the input data statistics. (Take for
	 *     example a binary file with poorly compressible code followed by
	 *     a highly compressible string table.) Smaller buffer sizes give
	 *     fast adaptation but have of course the overhead of transmitting
	 *     trees more frequently.
	 *   - I can't count above 4
	 */

	uInt last_lit;		/* running index in l_buf */

	ushf *d_buf;
	/* Buffer for distances. To simplify the code, d_buf and l_buf have
	 * the same number of elements. To use different lengths, an extra flag
	 * array would be necessary.
	 */

	ulg opt_len;		/* bit length of current block with optimal trees */
	ulg static_len;		/* bit length of current block with static trees */
	uInt matches;		/* number of string matches in current block */
	int last_eob_len;	/* bit length of EOB code for last block */

#ifdef DEBUG
	ulg compressed_len;	/* total bit length of compressed file mod 2^32 */
	ulg bits_sent;		/* bit length of compressed data sent mod 2^32 */
#endif

	ush bi_buf;
	/* Output buffer. bits are inserted starting at the bottom (least
	 * significant bits).
	 */
	int bi_valid;
	/* Number of valid bits in bi_buf.  All bits above the last valid bit
	 * are always zero.
	 */

	ulg high_water;
	/* High water mark offset in window for initialized bytes -- bytes above
	 * this are set to zero in order to avoid memory check warnings when
	 * longest match routines access bytes past the input.  This is then
	 * updated to the new high water mark.
	 */

} FAR deflate_state;

/* Output a byte on the stream.
 * IN assertion: there is enough room in pending_buf.
 */
#define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}

#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
/* Minimum amount of lookahead, except at the end of the input file.
 * See deflate.c for comments about the MIN_MATCH+1.
 */

#define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
/* In order to simplify the code, particularly on 16 bit machines, match
 * distances are limited to MAX_DIST instead of WSIZE.
 */

#define WIN_INIT MAX_MATCH
/* Number of bytes after end of data in window to initialize in order to avoid
   memory checker errors from longest match routines */

	/* in trees.c */
void ZLIB_INTERNAL _tr_init OF((deflate_state * s));
int ZLIB_INTERNAL _tr_tally OF((deflate_state * s, unsigned dist, unsigned lc));
void ZLIB_INTERNAL _tr_flush_block OF((deflate_state * s, charf * buf,
				       ulg stored_len, int last));
void ZLIB_INTERNAL _tr_align OF((deflate_state * s));
void ZLIB_INTERNAL _tr_stored_block OF((deflate_state * s, charf * buf,
					ulg stored_len, int last));

#define d_code(dist) \
   ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
/* Mapping from a distance to a distance code. dist is the distance - 1 and
 * must not have side effects. _dist_code[256] and _dist_code[257] are never
 * used.
 */

#ifndef DEBUG
/* Inline versions of _tr_tally for speed: */

#if defined(GEN_TREES_H) || !defined(STDC)
extern uch ZLIB_INTERNAL _length_code[];
extern uch ZLIB_INTERNAL _dist_code[];
#else
extern const uch ZLIB_INTERNAL _length_code[];
extern const uch ZLIB_INTERNAL _dist_code[];
#endif

#define _tr_tally_lit(s, c, flush) \
  { uch cc = (c); \
    s->d_buf[s->last_lit] = 0; \
    s->l_buf[s->last_lit++] = cc; \
    s->dyn_ltree[cc].Freq++; \
    flush = (s->last_lit == s->lit_bufsize-1); \
   }
#define _tr_tally_dist(s, distance, length, flush) \
  { uch len = (length); \
    ush dist = (distance); \
    s->d_buf[s->last_lit] = dist; \
    s->l_buf[s->last_lit++] = len; \
    dist--; \
    s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
    s->dyn_dtree[d_code(dist)].Freq++; \
    flush = (s->last_lit == s->lit_bufsize-1); \
  }
#else
#define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
#define _tr_tally_dist(s, distance, length, flush) \
              flush = _tr_tally(s, distance, length)
#endif

#endif				/* DEFLATE_H */
